A dielectric rod waveguide coupled with metal rectangular waveguide

Measurements have been done in the millimeter wave region on a composite waveguide which comprises a dielectric rod waveguide connecting two metal rectangular waveguides. Such a waveguide has been used by us in a Josephson harmonic mixer installed in a small metal cryostat, to prevent the thermal invasion from outside environment and to transmit both signal and LO waves with small losses. The measured transmission loss, that is caused mainly by the coupling loss between metal rectangular waveguides (TE₁₀ mode) and a dielectric rod waveguide (HE₁₁ mode), has been less than 2dB in the frequency range of 52–104 GHz.     

Cyclotron Resonance in the Hidden-Order Phase of URu_{2}Si_{2}

We report the first observation of cyclotron resonance in the hidden-order phase of ultraclean URu_{2}Si_{2} crystals, which allows the full determination of angle-dependent electron-mass structure of the main Fermi-surface sheets. We find an anomalous splitting of the sharpest resonance line under in-plane magnetic-field rotation. This is most naturally explained by the domain formation, which breaks the fourfold rotational symmetry of the underlying tetragonal lattice. The results reveal the emergence of an in-plane mass anisotropy with hot spots along the [110] direction, which can account for the anisotropic in-plane magnetic susceptibility reported recently. This is consistent with the "nematic" Fermi liquid state, in which itinerant electrons have unidirectional correlations.     

Preparation and characterization of single-phase SiC nanotubes and C-SiC coaxial nanotubes

Preparation conditions of single-phase SiC nanotubes and C-SiC coaxial nanotubes were investigated. The characterization of single-phase SiC nanotubes and C-SiC coaxial nanotubes were carried out. The SiC nanowires, which were made of the catenated SiC grains of 50–200 nm in diameter, were obtained in carbon nanotubes reacted at 1450 °C. The only C-SiC coaxial nanotubes were formed at 1300 °C. A few single-phase SiC nantoubes were synthesized at 1200 °C for 100 h. More than half number of nanotubes reacted at 1200 °C for 100 h were altered to single-phase SiC nantoubes by heat treatment of 600 °C for 1 h in air since the remained carbon was removed. The energy dispersive X-ray spectroscopy analysis revealed that the atomic ratio of Si to C in single-phase SiC nanotubes was almost 1; these single-phase SiC nanotubes consisted of near-stoichiometric SiC grains.     

Dependences of structural and electrical properties on thickness of polycrystalline Ga-doped ZnO thin films prepared by reactive plasma deposition

Polycrystalline Ga-doped (Ga content: 4 wt%) ZnO (GZO) thin films were deposited on glass substrates at 200 C by a reactive plasma deposition with DC arc discharge technique. The dependences of structural and electrical properties of GZO films on thickness, ranging from 30 to 560 nm, were investigated. Carrier concentration, n, and Hall mobility, μ, increases with increasing film thickness below 100 nm, and then the n remains nearly constant and the μ gradually increases until the thickness reaches 560 nm. The resistivity obtained of the order of 10⁻⁴ Ω cm for these films decreases with increasing film thickness: The highest resistivity achieved is 4.4×10⁻⁴ Ω cm with n of 7.6×10²⁰ cm⁻³ and μ of 18.5 cm²/V s for GZO films with a thickness of 30 nm and the lowest one is 1.8×10⁻⁴ Ω cm with n of 1.1×10²¹ cm⁻³ and μ of 31.7 cm²/V s for the GZO film with a thickness of 560 nm. X-ray diffraction pattern for all the films shows a hexagonal wurtzite structure with its strongly preferred orientation along the c-axis. Full width at half maximum of the (002) preferred orientation diffraction peak of the films decreases with increasing film thickness below 100 nm.